504 n. MARSHALL WARD. 



ripe oospore (a) differs from that of P. De Baryanum and 

 P. proliferiun, especially in entirely filling up the cavity 

 of the oogonium, the exospore becoming closely fitted to 

 the oogonium wall, and being indistinguishable from it, 

 except under favourable circumstances during development, 

 &c. After a few hours in fresh water the oospores observed 

 commenced to germinate in the usual manner (fig. 22b), and 

 the germinal tube either entered the substance of a favourable 

 matrix — flies' legs, meal worms, dead cress seedlings, &c. — or 

 proceeded to form zoospores (c) in a manner to be described 

 shortly. 



I made some observations on the particulars of growth and 

 entry of the germinal tube into a host-plant, which are illus- 

 trated by fig. 23 (a to/). After some hours, an oospore (a) 

 was seen to have germinated at some little distance from the 

 surface of a Cress-seedling (represented by x in the figure), 

 near which a minute unicellular alga was adherent; this 

 was at 11.10 a.m. At 11.30 one branch of the germinal tube 

 had grown rapidly (the others hardly elongating at all) and 

 extended {b) so as nearly -to touch the algal cell near the 

 cuticle of the seedling. Half-an-hour later, as shown at (c), 

 the apex of the hypha had touched and glided over the loose 

 algal cell, becoming sharply bent at right angles in doing so, 

 and displacing the cell somewhat from its original position. 

 So far the observation seems to show clearly that the extension 

 of the hypha takes place by apical growth only. The free 

 apex refusing to attach itself to the algal cell, then became 

 bent towards the surface of the seedling (d), and at 12.30 was 

 closely appressed to the cuticle. No intercalary growth had 

 occurred in those parts of the hypha behind the apex, as is 

 plain from the position of the angle and loose cell in (d) • 

 meanwhile, however, the apex became closely pressed against 

 the cuticle, apparently lifting the whole hypha slightly in the 

 ])rocess, and by ten minutes past one o'clock (e) it was clearly 

 making its Avay into the cell wall. At two p.m. the end had 

 completely perforated the cuticle and cell wall — not drawn \v\ f 

 — and had begun to extend vigorously inside. A slight inter- 



